Simplify the following expression: $ y = \dfrac{9z}{7z + 5} + 4 $
In order to add expressions, they must have a common denominator. Multiply the second expression by $\dfrac{7z + 5}{7z + 5}$ $ \dfrac{4}{1} \times \dfrac{7z + 5}{7z + 5} = \dfrac{28z + 20}{7z + 5} $ Therefore $ y = \dfrac{9z}{7z + 5} + \dfrac{28z + 20}{7z + 5} $ Now the expressions have the same denominator we can simply add the numerators: $y = \dfrac{9z + 28z + 20}{7z + 5} $ $y = \dfrac{37z + 20}{7z + 5}$